The present invention relates to a temperature control circuit for central processing units (CPUs) used for personal computers.
Conventionally, in order to prevent breakage and operational failure of a CPU, there are the method of cooling a heat-producing portion by a forced-air cooling fan and the method of improving the heat dissipation efficiency using a heat sink equipped on a heat-producing portion. However, these methods have the drawback of leading to an increase in weight and an increase in cost of the system.
On the other hand, the method is known of lowering the clock frequency and the power source voltage supplied to the CPU when the temperature of the CPU rises, thus suppressing the heat production from the CPU. However, in this prior art, since the clock frequency and the power source voltage are not switched controllably and properly, the operational specifications of the CPU are not satisfied during the switching operation, so that the CPU results often in its operational failure.
The present invention is made to solve the above-mentioned problems.
Moreover, the objective of the invention is to provide a circuit for controlling the temperature of a central processing unit (CPU). The CPU temperature control circuit can vary the clock frequency of the CPU and the power source voltage thereof while the operational specifications of the CPU are satisfied.
Another object of the present invention is to provide a method of controlling the temperature of a central processing unit.
The objective of the present invention is achieved by a temperature control circuit used for a central processing unit, wherein the temperature of the central processing unit is controlled, the central processing unit receiving clock pulses output from a clock generator and operating a power source voltage output from a power source circuit, comprising temperature measuring means for measuring the temperature of the central processing unit; a storage section for previously storing a reference value in temperature of the central processing unit; a comparator for comparing a measurement result of the temperature measuring means with the reference value stored in the storage section; and control means for switching a clock frequency from a high frequency to a low frequency when the temperature measurement result is larger than the reference value based on an output from the comparator and then switching the power source voltage from a high voltage to a low voltage, and for switching the power source voltage from a low voltage to a high voltage when the temperature measurement result is lower than the reference value and then switching the clock frequency from a low frequency to a high frequency.
In the temperature control circuit for a central processing unit, the control means comprises a first timer to which a changeover time of the clock frequency is previously set and a second timer to which a changeover time of the power source voltage is previously set. The clock frequency is switched based on an output from the first timer and the power source voltage is switched based on an output from the second timer.
In the temperature control circuit for a central processing unit, the control means comprises a third first timer to which the time the clock frequency changes from a high frequency to a first low frequency is previously set and a fourth timer to which the time the clock frequency changes from the first low frequency to a second low frequency is previously set. The power source voltage is switched from the high voltage to a first low voltage at the time the set time of the third timer has passed and the power source voltage is switched from the first low voltage to the second low voltage at the time the set time of the fourth timer has passed.
According to the second aspect of the present invention, a temperature control circuit used for a central processing unit, wherein the temperature of the central processing unit is controlled, the central processing unit receiving clock pulses output from a clock generator and operating on a power source voltage output from a power source circuit, comprising control means for switching the clock frequency from a high frequency to a low frequency when an external temperature control signal indicates a temperature drop and then switching the power source voltage from a high voltage to a low voltage, and for switching the power source voltage from a low voltage to a high voltage when the temperature control signal indicates a temperature drop release and then switching the clock frequency from a low frequency to a high frequency.
In the temperature control circuit for a central processing unit, the temperature control signal is a signal which notifies whether the central processing unit is driven by a battery or an ac adapter.
In the temperature control circuit for a central processing unit, the temperature control signal comprises an output of a register, the register being written by the central processing unit.
In the temperature control circuit for a central processing unit, the temperature control signal comprises an operation halt signal output to the central processing unit.
In the temperature control circuit for a central processing unit, the control means comprises a first timer to which the changeover time of the clock frequency is previously set, and a second timer to which the changeover time of the power source voltage is previously set. The clock frequency is switched based on an output from the first timer and the power source voltage is switched based on an output from the second timer.
According to the third aspect of the invention, a method of measuring the temperature of a central processing unit, the central processing unit receiving clock pulses output from a clock generator and operating on a power source voltage output from a power source circuit, comprises the steps of previously storing a reference value in temperature of the central processing unit; measuring the temperature of the central processing unit; comparing a measurement result with the reference value stored; switching a clock frequency from a high frequency to a low frequency when the temperature measurement result is larger than the reference value and then switching the power source voltage from a high voltage to a low voltage; and switching the power source voltage from a low voltage to a high voltage when the temperature measurement result is lower than the reference value and then switching the clock frequency from a low frequency to a high frequency.
In the temperature control method, the switching step comprises steps of previously setting a first time the clock frequency is changed and a second time the power source voltage is changed, and changing the clock frequency based on the first time and the power source voltage based on the second time.
In the temperature control method, the switching step comprises steps of previously setting a third time the clock frequency changes is changed from a high frequency to a first low frequency and a fourth time the clock frequency changes from the first low frequency to a second low frequency is previously set; changing the power source voltage from the high voltage to a first low voltage at the time the third time has passed, and changing the power source voltage from the first low voltage to the second low voltage at the time the fourth time has passed.
According to the fourth aspect of the invention, a method of measuring the temperature of a central processing unit, the central processing unit receiving clock pulses output from a clock generator and operating on a power source voltage output from a power source circuit, comprises the steps of switching the clock frequency from a high frequency to a low frequency when an external temperature control signal indicates a temperature drop and then switching the power source voltage from a high voltage to a low voltage; and switching the power source voltage from a low voltage to a high voltage when the temperature control signal indicates a temperature drop release and then switching the clock frequency from a low frequency to a high frequency.
In the temperature control method, the temperature control signal is a signal which notifies whether the central processing unit is driven by a battery or an ac adapter.
In the temperature control method, the temperature control signal comprises an output of a register, the register being written by the central processing unit.
In the temperature control method, the temperature control signal comprises an operation halt signal output to the central processing unit.
In the temperature control method, the switching step comprises steps of previously setting a first time the clock frequency is changed and a second time the power source voltage is changed; and changing the clock frequency based on the first time and the power source voltage based on the second time.